1. Field of the Invention
The present invention relates generally to inhibitors of nuclear transcription factor NF-.kappa.B, and the use of these inhibitors in the treatment of pathological conditions in humans. Specifically, the present invention relates to the inhibition of nuclear transcription factor NF-.kappa.B by Caffeic Acid Phenethyl Ester (CAPE); a 5, 6-dihydroxy, bicyclic derivative of CAPE; a 2, 5-dihydroxy derivative of CAPE; capsaicin (8-methyl-N-vanillyl-6-nonenamide); and resiniferatoxin, and methods for using these inhibitors in the treatment of pathological conditions such as toxic shock, acute inflammatory conditions, acute phase response, atherosclerosis and cancer.
2. Description of the Related Art
Nuclear Factor NF-.kappa.B is a protein specific to B cells and binds to a specific DNA sequence within the immunoglobin light chain .kappa. locus enhancer region. Members of the transcription factor NF-.kappa.B family have been identified in various organisms, ranging from flies to mammals (see Nolan, et al., Curr. Opin. Genet. Dev. 2:211-20(1992); Liou, et al., Curr. Opin. Genet. Dev. 5:477-87(1993); and Baeuerle and Henkel, Annu. Rev. Immunol. 12:141-79(1994)). Members of this transcription factor family are 35 to 61% homologous to each other and have a Rel homology domain of about 300 amino acids.
In mammals, the most widely distributed .kappa.B-binding factor is a heterodimer consisting of p50 and p65 (Rel-A) proteins. This transcription factor plays a central role in various responses, leading to host defense through rapid induction of gene expression. In particular, it controls the expression of various inflammatory cytokines, the major histocompatibility complex genes and adhesion molecules involved in tumor metastasis. Dysregulation of NF-.kappa.B and its dependent genes has been associated with various pathological conditions including toxic/septic shock, graft vs. host reaction, acute inflammatory conditions, acute phase response, viral replication, radiation damage, atherosclerosis, and cancer (see Baeuerle and Henkel, Annu. Rev. Immunol. 12:141-79 (1994); and Siebenlist, et al, Annu. Rev. Cell Biol. 10:405-55(1994)).
Unlike other transcription factors, the NF-.kappa.B proteins are held in the cytoplasm in an inactive state by an inhibitory subunit called I.kappa.Ba. The phosphorylation of I.kappa.B and its subsequent degradation allows translocation of NF-.kappa.B to the nucleus. This activation is induced by many agents, such as inflammatory cytokines (e. g., tumor necrosis factor (TNF), lymphotoxin (LT), and interleukin (IL)-1), mitogens, bacterial products, protein synthesis inhibitors, oxidative stress (H.sub.2 O.sub.2), ultraviolet light, and phorbol esters. Agents that can downmodulate the activation of NF-.kappa.B may be used for therapeutic treatment for these pathological conditions. The present invention is drawn to several such agents.
One agent is caffeic acid (3, 4-dihydroxy cinnamic acid) phenethyl ester (CAPE), a structural relative of flavonoids that is an active component of propolis from honeybee hives. It has antiviral, anti-inflammatory, and immunomodulatory properties, and has been shown to inhibit the growth of different types of transformed cells (see Grunberger, et al., Experientia 44:230-32 (1988); Burke, et al., J. Med. Chem. 38:4171-78(1995); Su, et al., Cancer Res. 54:1865-70 (1994); Su, et al., Mol. Carcinog. 4:231-42 (1991); Hlandon, et al., Arzneim.-Forsch./Drug Res. 30:1847-48 (1980); and Guarini, L., et al., Cell. Mol. Biol. 38:513-27 (1992)). In transformed cells, CAPE alters the redox state and induces apoptosis. Further, it has been reported that CAPE suppresses lipid peroxidation; displays antioxidant activity; and inhibits ornithine decarboxylase, protein tyrosine kinase, and lipoxygenase activities. CAPE can also inhibit phorbol ester-induced H.sub.2 O.sub.2 production and tumor promotion (see Bhimani, et al. , Cancer Res. 53:4528-33 (1993) and Frenkel, et al., Cancer Res. 53:1255-61 (1993)).
Another such downmodulating agent presented in this disclosure is capsaicin. Capsaicin is a homovanillic acid derivative (8-methyl-N-vanillyl-6-nonenamid) with a molecular weight of 305.42. It is an active component of the red pepper of the genus Capsicum, and has been used in humans for topical treatment of cluster headache, herpes zoster, and vasomotor rhinitis (see Holzer, P., Pharmacol. Rev. 43:143 (1994); Sicuteri, et al., Med. Sci. Res. 16:1079 (1988); Watson, et al., Pain 33:333 (1988); Marabini, et al., Regul. Pept. 22:1 (1988)). In vitro capsaicin modulates cellular growth, collagenase synthesis, and prostaglandin secretion from rheumatoid arthritis synoviocytes (see Matucci-Cerinic, et al., Ann. Rheum. Dis. 49:598 (1990)). Capsaicin has also been shown to be simmunomodulatory as indicated by its ability to modulate lymphocyte proliferation, antibody production, and neutrophil chemotaxis (see Nilsson, et al., J. Immunopharmac. 10:747 (1988); Nilsson, et al., J Immunopharmac. 13:21 (1991); and Eglezos, et al, J Neuroimmunol. 26:131 (1990)). These effects play an important role in capsaicin's use for treatment of arthritis. In addition, capsaicin induces mitochondrial swelling, inhibits NADH oxidase, induces apoptosis of transformed cells, stimulates adenylate cyclase, activates protein kinase C, inhibits superoxide anion generation and alters the redox state of the cell.
Various effects of capsaicin are mediated through a specific cellular receptor referred to as vanilloid receptor that is shared by resiniferatoxin. Like capsaicin, resiniferatoxin is an alkaloid derived from plants of the genus Euphorbia. Resiniferatoxin is a structural homologue of capsaicin (see FIG. 1). Resiniferatoxin is also structurally similar to phorbol esters (phorbol myristate acetate), which interacts with distinct binding sites and activates protein kinase C (see Szallasi, et al., Neurosci. 30:515 (1989); and Szallasi and Blumberg, Neurosci. 30:515 (1989)). Unlike resiniferatoxin, capsaicin has no homology to phorbol myristate acetate, but like resiniferatoxin, it too activates protein kinase C, suggesting that the latter activation is not due to the phorbol ester-like moiety on resiniferatoxin. Resiniferatoxin has been shown to mimic many of the actions of capsaicin.
Thus, inhibition of nuclear transcription factor NF-.kappa.B by Caffeic Acid Phenethyl Ester (CAPE); a 2,5-hydroxy derivative of CAPE; a 5, 6-dihydroxy, bicyclic derivative of CAPE, Capsaicin (8-methyl-N-vanillyl-6-nonenamide), and Resiniferatoxin is unknown in the prior art. The inhibition of NF-.kappa.B is an important step in the treatment of various pathological conditions which result from the activation of NF-.kappa.B by inflammatory cytokines, mitogens, oxidative stress, phorbol esters and other agents. The present invention fulfills a long-standing need and desire in the art to treat such pathological conditions.